Large servers require I/O expansion and the ability do add devices on-line. Expansion is typically very limited in bus-based I/O systems due to loading restrictions that limit the number of controllers on a single segment.
Networks obviate some of these problems assuring that expansion limits are not defined by arbitrary packaging constraints. However, expandability is enhanced if the network is hot-pluggable to allow on-line upgrades and repairs.
If the network has multiple modes of operation than a module being added must be configured in the mode of the modules it is connected. On-line addition or initialization of the module to the network would require that a service technician have knowledge of the modes of operation of the network and the ability to configure the module when it is added to the network.
Often, however, technicians are not sufficiently trained to perform such module configuration or the mode of a particular modules operation is not known. Accordingly, for multi-mode networks hot-pluggability is difficult to implement.